v0.5.1

• Feature: Support Promise cancellation for all connectors
  (#71 by @clue)

  $promise = $connector->create($host, $port);
  
  $promise->cancel();

• Feature: Add TimeoutConnector decorator
  (#51 by @clue)

  $timeout = new TimeoutConnector($connector, 3.0, $loop);
  $timeout->create($host, $port)->then(function(Stream $stream) {
      // connection resolved within 3.0s
  });